from The Century Dictionary and Cyclopedia

Etymologies

Examples

One minute you're learning that Sir Issac Newton chuckled only once in his life (scoffing at Euclidean geometry) and that the term for such people who don't laugh is 'agelast'; the next that the apparently nonsensical elephant jokes that were popular in the Sixties are believed to be racist in origin; the next how Bertrand Russell put down a heckler during one of his lectures on logic.

"Such (meta)satire not only labels Osborne a carnival agelast or unlaughing lenten hypocrite (Bakhtin 212-13) like Carroll's Queen of Hearts, but also suggests the dystopian undercurrents of carnival that post-Bakhtinians like Michael André Bernstein stress: 'when the tropes of Saturnalian reversal of all values spill over into daily life, they usually do so with a savagery that is the grim underside of their exuberant affirmations' (6)."Mark M. Hennelly (2009). ALICE'S ADVENTURES AT THE CARNIVAL. Victorian Literature and Culture, 37 , pp 103-128 (p 106)doi:10.1017/S106015030909007X

This word 'ultimately' and the infinitive ending on gelaein hide rather than illuminate the etymology. The root is gel- "laugh", with thematic ending -a- (this puts it into a subclass of verbs and shows up in many derivatives). Then gel-a-st- is an adjectival stem, showing up in gelast-os, -ê, -on "laughable" and the noun gelastês (feminine gelastria) "laugher, sneerer". With the negative prefix it is the adjective agelast-os, -ê, -on "unlaughing". It is this that Rabelais borrowed, dropping the ending as usual to fit it into French.